If you have a UK sim card with Vodafone READ THIS and check your bill...
(copied from another site)Roaming charges. I think we all know exactly what the UK mobile companies are going to do upon the UK leaving the EU and today I got confirmation. Received my bill which was £120 more than usual. Upon investigation I found that I had been charged for all calls made from EU after 29th March. Contacted Vodaphone and they said it was an error that had affected a small number of customers. My response was that I receive texts twice a week telling me that I have no roaming charges, so how come I get charged? They couldn't explain that. Additionally, it's going to take them up to 60 days to manually raise a credit. I'm still awaiting a response to my request to escalate this issue.

Interesting article (from February) on it here. It seems that Three (and a subsidiary) are the only people to rule roaming charges out. Companies are supposed to notify you if they intend to apply them again under certain circumstances.https://www.moneysavingexpert.com/news/ ... er-brexit/